#include<iostream>
using namespace std;
typedef long long LL;
const int N = 70;
LL dp[N][N];
int n, m;
void fun()
{
	for (int i = 0; i < N; i++) {
		for (int j = 0; j <= i; j++) {
			if (!j) {
				dp[i][j] = 1;
			}
			else {
				dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
			}
		}
	}
}
int main()
{
	fun();
	LL ans = 0;
	cin >> n >> m;
	for (int i = n; i <= m; i++) {
		ans += dp[m][i];
	}
	cout << ans << endl;
	return 0;
}